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When you trigger the fuel pump/ignition cutoff is it instant? The reason I ask is that if done that way you will be in for a whole bunch of hurt from the lawsuits. You can only disable those items on next start not in motion. On-Star tells the driver that they will starting the graduated shut down and slow the vehicle down but this is all done via the ecm since they have complete control over their ecm. The best way is at the starter the trigger wire going to soleniod. And now the newer cars are only sending a 3v signal from ignition switch so it's not enough power to trigger, also that ignition wire is now going to the ecm and the ecm is sending out the trigger to soleniod. I do GPS tracking for a living and have been doing it for 12 years now. Seen all the new productas that make it seem so easy to add these features but in the real world they are really not that practical to implement. No client will pay for the 6 hours labour to hookup all the door locks,window opening/closing engine disable. Unless your labour rates are cheap and you are doing the installs at your shop with a hoist. Food for thought SNO

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What redheadedrod is saying is if you cut off fuel while still having ignition connected will lean out the existing fuel left in the systems fuel lines and could cause problems. My concern is when you do that instantly cut either fuel or ignition you risk the lives of the driver of the vehicle as well as other's on the road. i.e highway speeds and car instantly shuts off vehicle could be in major traffic and cause accident or say they are passing someone and you cutoff everything (bad news). This may work well in India as the rules and regulation are not so controlled. In my area not many clients want to do it themselves and 3 hours labour will not complete 4 door lock/windows/fuel/ignition and starter disable along with the actual unit installation. I use mostly Enfora gps/gsm modems for my regular clients and the enfora's have 4 digital inputs 2 outputs and if thats not enough I can use the built-in pad to send out any data I need via the serial port. For my high-end clients I use Datalink's i50b satellite/gsm unit which has 3 serial ports and 4 analog/4digital in-out. I know most of these types of ideas come out of China. Have you seen how they get fuel levels? They say it's so easy but in reality you need to drop and drain fuel tank and drill a 1" hole in the top and add their float sensor (and hope you got all the metal filings out before you reinstall). Good luck on your project and I hope your sales are good. SNO

Pardon my brevity, but it's a subject I tend to avoid because I'm sick to death of the morons I encounter on this issue {admittedly only on Australian forums, and often involving the related dead issue of "oil pressure control of electric fuel pumps and fuel supply" (except for diesels)}.

As to the undesirable safety issue of cutting fuel supply etc, to me it's akin to cutting engines because of no/low oil pressure. Light an oil warning light or annunciator and let the intelligence of the driver decide if they want to kill the engine immediately, or get around the current drifted bend or off the railway crossing before killing the ignition/engine.

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Agreed! On my system for the rare customer that pays me to do it (he's a small buy here/pay here car dealership), I disable starter but it is only on next start . He has never had to use that part of the system in 3 years. Now for theft its very good to have, but the better thing to have is a backup battery in a different location from the tracking unit and wired seperately to continue powering the unit so it can be tracked in a theft. Most of my installs are so hidden I even have a hard time finding them when client refreshes his fleet. I hate the thought of me selling a tracking unit to a client and the vehicle gets stolen but first thing the thief does is cut wires of an antenna or power. For a special purpose I have even installed 2 separate units in the same vehicle (trucking company hauling narcotics). Food for thought SNO

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Put it this way, it amazes me how many alarmed vehicles did NOT have backup batteries. And that was BEFORE trackers entered the picture.
Of course satellite horns solved many of the alarm issues, but to have a tracker only to have the thief hide the vehicle and disconnect the battery...

As to dual systems, have I ever mentioned how much I like redundancy?
As for trackers, many expect one but rarely two. Of course a well hidden tracker with ONE obvious battery/supply and well concealed secondary (or is that tertiary?) power source may overcome the need for the expense of second tracker. But full redundancy means a second tracker - ie, if the first is found or fails. (And that should be triggered after a delay after the first quits/fails - just in case scanners are used. And it should operate intermittently...)

Funny how technology changes, but not the basic principles.
As a wise turkey once said - "[i]everything is the same... just different[i]".

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Lets look at the situation. Lean burning is a killer to an engine. If you have a race engine not getting enough gas it will blow the engine in short order. I would be surprised if cars such as NASCAR vehicles don't automatically cut the ignition on a loss of fuel pressure. At a drag strip you are very likely to blow your engine if not getting enough gas while doing that 1/4mile run at WOT. Losing your ignition doesn't harm your engine as far as I know. If you do cut the gas you HAVE to also cut the ignition as well to protect the engine. At WOT you CAN easily blow the engine cutting the fuel pump without cutting the ignition since you are slowly bleeding off the pressure and running for a few more cycles. If you cut the injectors it may be different since no fuel is being injected. And most waste spark systems will spark on an empty cylinder..

And as otherwise stated cutting power while running down the road is dangerous and will leave the maker of the device liable for damages caused by accidents caused by shutting down the engine while moving. The Proper way to do this is to cut the ignition when the car has come to a complete stop. I would probably also make sure the brake pedal is applied to ensure the car is not rolling still.

As to secure connections.. You could have your vehicle check in every so often and if it doesn't get a signal to shut its self down and to prevent any starting etc. So hiding it wouldn't accomplish much.

My security system will have multiple backup batteries as will my CarPC... Plus they will talk to each other making any attempts to steal the vehicle very annoying to the thief.

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I know this is old but I just want to say something. a gas engine is turned off by cutting spark. A diesel is turned off by cutting fuel. If those two methods are used respectively then the engine should not blow up since that's the same way it is turned off when the ignition is turned off. Yes granted if its still in gear when the engine is turned off it may damage the engine but not too bad unless its done regularly.